public class TestDemo {
    public static void main(String[] args) {
        int i = 0;
        float sum = 0 ;
        for (i = 1; i <= 100 ; i++) {
            if(i%2 != 0){
                sum += 1.0/i;
            } else{
                sum -= 1.0/i;
            }
        }
        System.out.println(sum);
    }
}
